In an internal combustion engine for a vehicle generally has an exhaust gas recirculation (EGR) system to meet the exhaust gas regulations. In particular, in a diesel engine, the exhaust gas regulations require to reduce the amount of particulate matter to a certain level. As one method, the amount of particulate matter can be reduced by reducing fuel consumption amount using the EGR system.
The EGR system returns some of the exhaust gas exhausted from an engine to an intake device of a cylinder to lower combustion temperature of the engine and to decrease NOx thereof, and an EGR valve and an EGR cooler are disposed such that the EGR gas is cooled to a predetermined temperature to be supplied to the intake manifold.
A rotational speed of the engine and the fuel injection amount are applied and the EGR valve is controlled by a feed forward control method so as to control the flux of the EGR gas, and a mass air flow sensor (MAF) detects the flux of the EGR gas.
The flux of the EGR gas that is determined by the rotational speed and the fuel injection amount of the engine can be varied by several factors such that the flow of the EGR gas cannot be reflected and a feedback control can be interfered in a particular condition. It is further difficult to overcome a time delay due to a response speed of a EGR flow path and various sensors. In addition, it is difficult to accurately estimate the EGR rate when there is an element that changes intake and exhaust pressures, such as a variable intake and exhaust valve and a turbocharger.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.